Mostly found in western Canada and USA. Black is found
in southern Ontario. Brown is found mostly in the western areas
of southern Ontario. Russian is known to occur in central Ontario.
Spotted can be found throughout Southern Ontario especially
in Grey and Hastings. Diffuse is not commonly found in Ontario.
Frequently grows in shallow top soil areas.

Growth Habit

Perennial, Spotted is biennial or short lived perennial

Method of Propagation

Seeds

Control

Very difficult to control. Not listed on any labels except
for diffuse knapweed on the Banvel label. Close mowing at the
bud or flowering stage can reduce infestation (June to October)
but flowering stems may regrow. Shallow cultivation is not effective
but deep plowing (18 cm) followed by vigorous establishment
of grasses can reduce the infestation.

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